1. Field of the Invention
This invention relates in general to submersible pump motors, and in particular to a bearing which resists rotation. The bearing supports the shaft in the motor.
2. Description of the Prior Art
A submersible pump assembly of the type herein has a centrifugal pump driven by a submersible pump motor, which may include more than one motor in tandem. The motors may total when assembled up to sixty feet in length and be rated at several hundred horsepower. Each motor has a stator secured within a tubular housing. The stator is made up of thin disks, called laminations, that are magnetic and insulated from each other by coatings. Windings extend through the laminations of the stator.
A rotor secured to a shaft rotates within the stator. Because of the long length, the rotor is made up of a number of rotor sections. Each rotor section comprises a large number of flat metal disks, called laminations, that are secured by copper rods. The disks are insulated from each other by coatings. The rotor sections are spaced apart from each other, and a bearing assembly locates between each rotor section for maintaining the shaft in axial alignment. The rotor sections are keyed to the shaft for rotation with the shaft.
Each bearing assembly includes a bushing keyed to the shaft for rotation. A bearing body fits slidingly on the bushing and frictionally engages the inner wall of the stator at operating temperatures. This engagement prevents the bearing body from rotating and supports the shaft in alignment. One type of bearing body employs a resilient member on the exterior for engaging the stator.
The bearing body typically is a steel member that is magnetic. Unless provided for, the stator would interact with the bearing body to create eddy currents, which are not desirable. The electromagnetic field of the stator would try to rotate the bearing body, creating heat and power losses. In the prior art, to avoid magnetic interaction with the bearing body, the stator utilizes sections of brass laminations located adjacent each bearing. The brass, being nonmagnetic, reduces electromagnetic interaction with the bearing body. The remainder of the stator would be made up of steel laminations. However, the brass laminations are expensive and wear more quickly than the steel laminations. Plastic bearing bodies have been proposed, but plastic bearings have temperature limitations.